openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 110 insertions, 0 deletions

diff --git a/security/tomoyo/load_policy.c b/security/tomoyo/load_policy.c
new file mode 100644
index 000000000..363b65be8
--- /dev/null
+++ b/security/tomoyo/load_policy.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * security/tomoyo/load_policy.c
+ *
+ * Copyright (C) 2005-2011  NTT DATA CORPORATION
+ */
+
+#include "common.h"
+
+#ifndef CONFIG_SECURITY_TOMOYO_OMIT_USERSPACE_LOADER
+
+/*
+ * Path to the policy loader. (default = CONFIG_SECURITY_TOMOYO_POLICY_LOADER)
+ */
+static const char *tomoyo_loader;
+
+/**
+ * tomoyo_loader_setup - Set policy loader.
+ *
+ * @str: Program to use as a policy loader (e.g. /sbin/tomoyo-init ).
+ *
+ * Returns 0.
+ */
+static int __init tomoyo_loader_setup(char *str)
+{
+	tomoyo_loader = str;
+	return 1;
+}
+
+__setup("TOMOYO_loader=", tomoyo_loader_setup);
+
+/**
+ * tomoyo_policy_loader_exists - Check whether /sbin/tomoyo-init exists.
+ *
+ * Returns true if /sbin/tomoyo-init exists, false otherwise.
+ */
+static bool tomoyo_policy_loader_exists(void)
+{
+	struct path path;
+
+	if (!tomoyo_loader)
+		tomoyo_loader = CONFIG_SECURITY_TOMOYO_POLICY_LOADER;
+	if (kern_path(tomoyo_loader, LOOKUP_FOLLOW, &path)) {
+		pr_info("Not activating Mandatory Access Control as %s does not exist.\n",
+			tomoyo_loader);
+		return false;
+	}
+	path_put(&path);
+	return true;
+}
+
+/*
+ * Path to the trigger. (default = CONFIG_SECURITY_TOMOYO_ACTIVATION_TRIGGER)
+ */
+static const char *tomoyo_trigger;
+
+/**
+ * tomoyo_trigger_setup - Set trigger for activation.
+ *
+ * @str: Program to use as an activation trigger (e.g. /sbin/init ).
+ *
+ * Returns 0.
+ */
+static int __init tomoyo_trigger_setup(char *str)
+{
+	tomoyo_trigger = str;
+	return 1;
+}
+
+__setup("TOMOYO_trigger=", tomoyo_trigger_setup);
+
+/**
+ * tomoyo_load_policy - Run external policy loader to load policy.
+ *
+ * @filename: The program about to start.
+ *
+ * This function checks whether @filename is /sbin/init , and if so
+ * invoke /sbin/tomoyo-init and wait for the termination of /sbin/tomoyo-init
+ * and then continues invocation of /sbin/init.
+ * /sbin/tomoyo-init reads policy files in /etc/tomoyo/ directory and
+ * writes to /sys/kernel/security/tomoyo/ interfaces.
+ *
+ * Returns nothing.
+ */
+void tomoyo_load_policy(const char *filename)
+{
+	static bool done;
+	char *argv[2];
+	char *envp[3];
+
+	if (tomoyo_policy_loaded || done)
+		return;
+	if (!tomoyo_trigger)
+		tomoyo_trigger = CONFIG_SECURITY_TOMOYO_ACTIVATION_TRIGGER;
+	if (strcmp(filename, tomoyo_trigger))
+		return;
+	if (!tomoyo_policy_loader_exists())
+		return;
+	done = true;
+	pr_info("Calling %s to load policy. Please wait.\n", tomoyo_loader);
+	argv[0] = (char *) tomoyo_loader;
+	argv[1] = NULL;
+	envp[0] = "HOME=/";
+	envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
+	envp[2] = NULL;
+	call_usermodehelper(argv[0], argv, envp, UMH_WAIT_PROC);
+	tomoyo_check_profile();
+}
+
+#endif